The Colorado River Basin is managed in a complex and multi-level legal structure that involves many stakeholders. The Colorado River watershed is divided into the Upper and Lower Basins. The Upper Basin includes the states of Wyoming, Colorado, Utah and New Mexico. The Lower Basin includes Arizona, California and Nevada. A binational treaty governs the releases to Mexico from the Colorado River.

Within the overall structure of the Law of the River, the basin states and the Boulder Canyon Project Act water contractors must work collectively to address their water supply issues. In the Lower Basin, water supplies are administered by a federal water master, designated by the Secretary of the Interior working through the Bureau of Reclamation. In the Upper Basin, the Upper Colorado River Commission serves in the role of administering compliance with the 1922 Colorado River Compact. In addition, every basin also has its own unique set of law governing rights that apply within those states.

The 2007 Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for both Lake Powell and Lake Mead are set to expire in 2026. The seven Colorado River Basin states and stakeholders must work together to develop the new criteria that will replace those guidelines. At present, there is a gridlock in those negotiations between the Upper and Lower Basin states and it must be resolved in 2025 to replace those guidelines expiring in 2026.

As part of the 2025 SW Ag Summit program on Thursday, 20 February on the campus of Arizona Western College, two sessions will be held addressing the future of the Colorado River and management plans for water allocations that will be very important for agriculture in the lower Colorado River Valley in the next decade. This will include a keynote session in the morning and a breakout session will follow. The schedule for these two sessions is listed below.

Keynote Program, 7:30 a.m., 20 February 2025, College Community Center (3C)

The Future of the Colorado River

• Jeff Silvertooth, University of Arizona
• Tom Buschatzke, Director at Arizona Department of Water Resources
• J.B. Hamby, Chairman of the Colorado River Board of California and Colorado River Commissioner

 

Breakout Session – Colorado River Update, 9:30 a.m. MAC 106

Outlook on Basin wide Negotiations for the 2026 Operational Guidelines

• Introduction – Jeff Silvertooth, Moderator, University of Arizona
• Colorado River Perspectives - Principal and Water User Discussion
• Hank Auza, President, Yuma County Water Users Association
• Elston Grubaugh, General Manager, Wellton-Mohawk Irrigation and Drainage District
• J.B. Hamby, Chairman | Colorado River Board of California and Colorado River Commissioner | State of California
• Tom Buschatzke, Director, Arizona Department of Water Resources

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Meerkat’ was seeded, then sprinkler-irrigated to germinate seed Jan 13, 2025 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂ backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.

Downy mildew (caused by Peronospora farinosa f. sp. spinaciae)was first observed in plots on Mar 5 and final reading was taken on March 6 and March 7, 2025. Spray date for each treatments are listed in excel file with the results.

Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft²areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft²area of bed was approximately 144. The percentage were then changed to 1-10scale, with 1 being 10% infection and 10 being 100% infection.

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided most effective control against the disease include Orondis ultra, Zampro, Stargus, Cevya, Eject .Please see table for other treatments with significant disease suppression/control.  No phytotoxicity was observed in any of the treatments in this trial.

With harvest season in full swing, I thought I would share with you an observation I’ve made over the years. I’ve noticed that gulls seem to congregate around fields being harvested. I am not sure what the attraction is, but my guess is that they are begging for food from harvest crews. Gulls are problematic in that they are known to be carriers of several human pathogens including E. coli O157, Salmonella and Campylobacter (Jay-Russell,2013). When gulls fly over fields, it is inevitable that some of their fecal matter will be deposited on unharvested crops, in irrigation canals and on harvest equipment (Figs 1-4). Obviously, when this happens, it is a food safety risk. Despite the significant effort and investment made in bird deterrent technologies, I am not aware of any that are effective and reasonably priced for gulls. The best advice I have for reducing the risk of food contamination from gulls is to be vigilant about instructing workers not to feed the birds and locate food trucks away from crops to be harvested.

References
Jay-Russell, M.T. (2013). What is the risk from wild animalsin food-borne pathogen contamination of plants?. CABI Reviews 4(8),1-16.https://doi: 10.1079/PAVSNNR20138040

Fig. 1. Bird fecal matter on romaine lettuce.


Fig. 2. Gull flying over romaine lettuce being harvested.


Fig. 3. Gulls flying over irrigation canal near lettuce field
being harvested.


Fig. 4. Bird fecal matter on lettuce harvesting equipment.

We are planning some Broccoli herbicide trials at the Yuma Agricultural Center. The idea is to have some demonstration plots for you to come and visit.  Will evaluate new and old products with different rates and incorporation methods hoping to obtain additional data on phytotoxicity and weed control. The goal is to have the demo plots available to PCAs and growers at the Yuma Agricultural Center as well as document the observations and make them available to all people in the industry.
Do you have an idea of a treatment or combination that could possibly perform great for our weed complex? If you like to participate creating this protocol please send us your ideas and suggestions. As an example we could play with older products such as Treflan, Prefar, Prowl, Devrinol, Goal Tender, Clethodim etc. Some suggest different levels of sprinkler incorporation (8, 12, 24, 36 hours) for Devrinol. Others apply Treflan to flat ground then disk and put beds, come back with Goal, or Clethodim.
 If you like to include a treatment please send it to marcop@ag.arizona.edu

Included below is a list of organic insecticides that you can consider for your organic IPM programs. Although there are few alternative organic insecticide options, it is important to rotate when possible. Like conventional insecticides, continuous exposure to the same biopesticides may pose some risk of further reducing their efficacy and leading to the development of resistance. 

A good organic insecticide rotation practice is to alternate selective organic insecticides with broad-spectrum organic insecticides. The use of selective organic insecticides favors the increase of beneficial arthropod populations which may help to keep the pest population in check and delay repeated application of insecticides. When the population of lepidopteran pests is low, spraying Bt-based insecticides first and pyrethrin or Spinosad-based products thereafter is a good strategy. Proper insecticide rotation is important because it can help reduce insecticide application frequency, resulting in reduced crop production costs. 

 Tank-mixing can help improve the efficacy of some organic insecticides against some target pests. Tank-mixing a Bt insecticide with pyrethrin, such as Xentari + Pyganic or Dipel + Pyganic, can be an effective combination for controlling lepidopteran larvae. Additionally, combining Pyganic and a neem-based insecticide like Aza-Direct can be a favorable combination for small lepidopteran larvae. Tank-mixing Entrust (spinosad) and M-Pede can help suppress flea beetles and bagrada bugs.

Lake Mead, the nation’s largest reservoir, continues to decline to historic lows, posing a critical hydrological challenge in the Southwest with significant implications for Arizona agriculture. Prolonged and severe drought across the Colorado River Basin has led to cascading water-use reductions, including a Tier 1 shortage that has cut central Arizona’s agricultural water allocations by 65%.

The drought situation in Arizona has intensified significantly since late 2024 (see Figures 1 & 2 to determine the differences in extreme drought expansion), with extreme drought (D3) conditions spreading across much of the state. Yuma, La Paz, Maricopa, Gila, and now Greenlee counties are fully engulfed in D3 drought, while the expansion has also reached parts of Pima, Mohave, Yavapai, Navajo, Apache, Santa Cruz, Graham, and Cochise counties. This alarming trend signals a severe water deficit, raising serious concerns about its impact on agriculture, water resources, ecosystems, and communities statewide. This crisis underscores the urgent need for innovative strategies to sustain agriculture and secure water resources in the region.

One approach to addressing this crisis is implementing conservative water management, which includes adopting advanced soil moisture monitoring technologies. This raises an important question: How do you select the right soil moisture sensors for irrigation management decisions?

A wide range of soil moisture sensors are commercially available for agricultural use. However, selecting the most suitable sensor for Yuma’s arid environment, where soils are characterized by a pH greater than 8 requires careful consideration of key criteria. The selection process should focus on two critical aspects:

(a) Operational Feasibility:

• Telemetry: Real-time data transmission capabilities for remote monitoring.
• Sensor Cost: Affordability and long-term investment viability.
• Data Logging Cost: Expenses associated with data storage and accessibility.
• Ease of Operation: User-friendliness, installation requirements, and integration with existing systems.

(b) Performance Accuracy:

• Orientation: Proper sensor placement based on soil type, whether horizontal or vertical, to ensure accurate readings.

Calibration: Consideration of factory calibrations versus site-specific calibrations for improved measurement precision.

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts down in all traps over the last month; about average for December.

Beet armyworm: Moth trap counts decreased in all areas in the last 2 weeks but appear to remain active in some areas, and average for this time of the year.

Cabbage looper: Moths increased in the past 2 weeks, and average for this time of the season.

Diamondback moth: Adults increased in several locations last, particularly in the Yuma Valley most traps.  Below average for December.

Whitefly: Adult movement remains low in all areas, consistent with previous years 

Thrips: Thrips adult movement continues to decline, overall activity below average for December.

Aphids: Winged aphids still actively moving but declined movement in the last 2 weeks. About average for December.

Leafminers: Adult activity down in most locations, below average for this time of season.